add environment variable validation with Joi in opsce module

backend/src/opsce/opsce.module.ts

@@ -1,12 +1,37 @@
 import { Module } from '@nestjs/common';
-import { AssetsModule } from './assets/assets.module';
-import { DepartmentsModule } from './departments/departments.module';
-import { AuditModule } from './audit/audit.module';
-import { UsersModule } from './users/users.module';
-import { LocationsModule } from './locations/locations.module';
+import { ConfigModule } from '@nestjs/config';
+import { AssetsModule } from '../assets/assets.module';
+import { DepartmentsModule } from '../departments/departments.module';
+import { AuditModule } from '../audit/audit.module';
+import { UsersModule } from '../users/users.module';
+import { LocationsModule } from '../locations/locations.module';
 
+/**
+ * OpsceModule
+ *
+ * Aggregates all operational sub-modules: users, locations, audit, and
+ * departments. ConfigModule is already global (registered in AppModule), so
+ * every sub-module can inject ConfigService without re-importing it here.
+ */
 @Module({
-  imports: [UsersModule, LocationsModule, AuditModule, DepartmentsModule],
-  exports: [UsersModule, LocationsModule, AuditModule, DepartmentsModule],
+  imports: [
+    // ConfigModule is global — listed here for explicit documentation only.
+    // Remove this import if it causes duplicate-module warnings in your version
+    // of @nestjs/config.
+    ConfigModule,
+
+    UsersModule,
+    LocationsModule,
+    AuditModule,
+    DepartmentsModule,
+    AssetsModule,
+  ],
+  exports: [
+    UsersModule,
+    LocationsModule,
+    AuditModule,
+    DepartmentsModule,
+    AssetsModule,
+  ],
 })
-export class OpsceModule {}
+export class OpsceModule {}